Extraction of Thorium(IV) with N-Methyl-N,N,N-trioctylammonium Chloride from Monazite Acidic Leach Liquor and Its Use for Spectrophotometric Determination

N-Methyl-N,N,N-trioctylammonium chloride was applied for selective extraction and separation of thorium. The Th extraction and stripping conditions were experimentally optimized. 0.75 M N-methyl-N,N,N-trioctylammonium chloride was found to be suitable for the Th separation. The extraction of Th(IV) form monazite is an exothermic process. The optimum parameters were applied to the spectrophotometric determination of Th using Thoron I at λ_max = 540 nm with accurate results. From the stripped liquor (1 M HNO₃), Th was precipitated as thorium oxalate for technological application. Thus, marketable pure thorium product was prepared in addition to uranium and rare earth concentrates.

     

A critical synthesis of thermophysical characteristics of nanofluids

A critical synthesis of the variants within the thermophysical properties of nanofluids is presented in this work. The experimental results for the effective thermal conductivity and viscosity reported by several authors are in disagreement. Theoretical and experimental studies are essential to clarify the discrepancies in the results and in proper understanding of heat transfer enhancement characteristics of nanofluids. At room temperature, it is illustrated that the results of the effective thermal conductivity and viscosity of nanofluids can be estimated using the classical equations at low volume fractions. However, the classical models fail to estimate the effective thermal conductivity and viscosity of nanofluids at various temperatures. This study shows that it is not clear which analytical model should be used to describe the thermal conductivity of nanofluids. Additional theoretical and experimental research studies are required to clarify the mechanisms responsible for heat transfer enhancement in nanofluids. Correlations for effective thermal conductivity and viscosity are synthesized and developed in this study in terms of pertinent physical parameters based on the reported experimental data.     

The effect of environmental exposure upon the mechanical properties of coir or oil palm fiber reinforced composites

Polyester matrix composites reinforced using nonwoven coir or oil palm empty fruit bunch fiber mats were manufactured. Fibers were used unmodified, chemically modified by acetylation, or treated with silane or titanate coupling agents. Composite test pieces were exposed to decay fungi in unsterile soil for up to 12 months, along with samples made of unreinforced, or glass fiber reinforced, resin. Water exposure tests were also performed. The effect of such exposure on the mass loss, tensile and flexural properties of the samples was evaluated. Mechanical properties deteriorated as a result of exposure. However, acetylation of fibers, or treatment with silane coupling agent was found to afford a significant degree of protection. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1322–1330, 2000     

Rapid idea of located defects on grounding systems

This study gives an original way to have a rapid idea of the position of the located defects on grounding systems. For determining electromagnetic fields' radiation, we use an easy method, based on analytical formula, transmission line theory, and modified images theory, instead of complex method of Summerfield's integrals. The cartography of the electromagnetic fields radiated at the soil—air interface, by energized grounding systems (electrode or grid), can be used to detect and localize a defect on these systems. This model is aimed at helping in electromagnetic compatibility and lightning protection studies. Copyright © 2011 John Wiley & Sons, Ltd.     

Uplink and downlink scheduling for point to multipoint WiMAX Networks

IEEE 802.16 standard lacks a Media Access Control (MAC) scheduling architecture to enforce Quality of Service (QoS) requirements of different services classes. In this paper, we propose an opportunistic and optimized scheduler that meets connections' QoS requirements while it pledges fairness among admitted connections. Our approach involves separating the scheduling problem into two sub‐problems. In the first sub‐problem, which addresses interclass time‐slots allocation, the proposed scheduler calculates the optimum number of time‐slots in each time frame corresponding to the service classes with the objective of minimizing the blocking probability of each class. In the second sub‐problem, the intraclass slot allocation problem, time‐slots for each class are allocated using an integrated cross‐layer priority functions (PFs) that provide proportional fairness among a class connections. The simulation results reveal that the proposed scheduler realizes our objectives, and provides efficient QoS scheduling without starving the connections of the BE class. Copyright © 2008 John Wiley & Sons, Ltd.     

Thermal and high hydrostatic pressure inactivation of myrosinase from green cabbage: A kinetic study

Myrosinase, a family of enzymes which coexist with glucosinolates in all Brassica vegetables, catalyses the hydrolysis of glucosinolates to yield compounds that can have beneficial effects on human health. In this study, the thermal and pressure inactivation of myrosinase from green cabbage was kinetically investigated. Thermal inactivation started at 35 °C and inactivation kinetics was studied in the temperature range 35-55 °C. Thermal inactivation of green cabbage myrosinase followed the well known consecutive step model. Pressure inactivation started at 300 MPa, even at 10 °C, and the consecutive step model effectively described pressure inactivation in the range 300-450 MPa at 10 °C. The combined effects of applying various pressures and temperatures on myrosinase inactivation kinetics were studied in the ranges 35-50 °C and, 100-400 MPa. The inactivation followed first-order kinetics at all of the applied combinations. This study demonstrates that myrosinase from green cabbage is highly susceptible to both thermal and high pressure processing. Furthermore, it is also noted that myrosinase stability during processing appears to vary widely between different Brassica species.     

A framework for managing organizations in complex environments

The complex environments of today’s markets makes managing organizations in complexity and turbulence a concern for senior managers, and necessitate developing a dynamic strategic framework to cope with complexity in managing organizations. This paper demonstrates a study that was conducted to value a structured set of management principles and sub-elements by a panel of experts to develop a conceptual framework to manage in complex and very high dynamic environments. The panel consisted of 22 senior level managers of grade “A” companies in the construction industry in Qatar State using a two-round Delphi technique. The study developed two frameworks. The first framework is for managing complexity in the construction sector. The second one is the primary general framework, which forms a basis for a generalized framework for other industries. This study participates in developing valuable management practices in complex environments to tackle uncertainty, unpredictability, disorder, rapid changes and non-linearity, which would be of great help for leaders, senior managers and practitioners who operate in complex environments.     

A Self-Optimizing QoS-Based Access for IoT Environments

Nowadays, providing Internet of Things (IoT) environments with service level guarantee is a challenging task. Moreover, IoT services should be autonomous in order to minimize human intervention and thus to reduce the operational management cost of the corresponding big scale infrastructure. We describe in this paper a service level-based IoT architecture enabling the establishment of an IoT Service Level Agreement (iSLA) between an IoT Service Provider (IoT-SP) and an IoT Client (IoT-C). The proposed iSLA specifies the requirements of an IoT service, used in a specific application domain (e-health, smart cities, etc.), in terms of different measurable Quality of Service (QoS) parameters. In order to achieve this agreement, several QoS mechanisms are to be implemented within each layer of the IoT architecture. In this context, we propose an adaptation of the IEEE 802.15.4 slotted CSMA/CA mechanism to provide different IoT services with QoS guarantee. Our proposal called QBAIoT (QoS-based Access for IoT) creates different Contention Access Periods (CAP) according to different traffic types of the IoT environment. These CAPs are QoS-based and enable traffic differentiation. Thus, a QoS CAP is configured with several slots during which only IoT objects belonging to the same QoS class can send their data. Furthermore, we specify a self-management closed control loop in order to provide our IoT architecture with a self-optimizing capability concerning QoS CAPs slots allocation. This capability takes into account the actual usage of QoS CAPs as well as the characteristics of the corresponding traffic class.